feat: GPS route simulation — travel to ... over N seconds (FP-6)

[pbertsch]

Summary

Implements FP-6: GPS route simulation, matching Maestro's travel command — a way to walk the device's GPS location through an ordered list of waypoints over time, simulating movement for maps/delivery/rideshare/fitness test flows.

New syntax:

travel to
  37.7749, -122.4194
  37.7849, -122.4094
over 10 seconds

• An ordered, indented list of lat, lng waypoints under travel to, followed by an optional sibling over N seconds clause at the same indent level (same trailing-clause shape with examples: uses after a test body).
• over N seconds is optional; omitting it defaults to ~1 second per leg of the route instead of jumping instantly.
• This is pure orchestration on top of the existing single-point SetLocation primitive — the executor linearly interpolates between consecutive waypoints and calls SetLocation repeatedly at ~1-second intervals (never tighter, to avoid hammering adb/simctl). No new device-level GPS integration was added.
• Follows the same physical-device exclusion set location already has: skips with a single warning on real devices (checked once up front in DeviceContext.Travel, not once per interpolated frame).

What changed

• internal/parser/token.go, ast.go, parser.go — new TOKEN_TRAVEL/TOKEN_OVER tokens, Waypoint/TravelStep AST nodes, parseTravel/parseWaypoints. Extracted parseCoordinateLine out of parseActionSetLocation so both set location and travel to share the exact same "lat, lng" token-reconstruction logic (no duplicated coordinate parsing).
• internal/runner/device_context.go — DeviceContext.Travel + buildTravelRoute (pure interpolation math with no device I/O, so it's unit-testable without a real or faked adb/simctl).
• internal/runner/executor.go — dispatch case, stepDescription, runTravel (validates waypoint count and parses lat/lng before touching the device, mirroring the cloud-mode skip pattern other DeviceContext-only verbs use).
• Docs: website/src/content/docs/probescript/dictionary.md, syntax.md, platform/android.md, comparisons/patrol-alternative.md, README.md, CHANGELOG.md ([Unreleased]).
• MCP: internal/mcp/server.go (write_test tool description) and website/src/content/docs/tools/mcp.md (new "GPS route simulation" example session) — per this repo's MCP Server Coverage rule.

Test plan

• go build ./... — passes
• go test ./... — passes, summary below
• staticcheck ./... — clean, no new issues
• go vet ./... — clean
• Parser tests: waypoint parsing (2 and 3 waypoints), negative coordinates (same PT-24-class regression guard as set location), optional over clause, malformed-waypoint parse error, sibling step after the block still parses correctly
• Executor tests: buildTravelRoute interpolation math (frame/gap counts, exact endpoint landing, default-duration fallback, degenerate <2-waypoint case), cloud-mode skip (nil deviceCtx), waypoint-count validation error, invalid-coordinate error, stepDescription output
• NOT verified against a real emulator/simulator or physical device. This sandbox has adb and xcrun binaries present but no running emulator/simulator/device to actually drive — I did not claim or fake real-device verification. Everything above is unit/parser/executor-level coverage only; before shipping this in a release, it should be live-verified against a real Android emulator and iOS simulator the way recent CHANGELOG entries for set location document (e.g. "Live-verified fixed against a real emulator").

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ok  	github.com/alphawavesystems/flutter-probe/internal/ai	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/cli	0.606s
ok  	github.com/alphawavesystems/flutter-probe/internal/cloud	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/config	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/device	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/ios	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/mcp	0.842s
ok  	github.com/alphawavesystems/flutter-probe/internal/migrate	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/parser	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/plugin	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/probelink	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/redact	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/report	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/runner	(cached)
ok  	github.com/alphawavesystems/flutter-probe/internal/visual	(cached)

Out of scope for this PR (flagged, not implemented): the Maestro migration converter (internal/migrate) does not yet map Maestro's own travel: YAML step to this new syntax — it would currently fall through to a TODO comment like any other unmapped construct. Happy to follow up in a separate PR if wanted.